(The S in this name is pronounced like 's' in 'so', TH and TH both are pronounced like 'th' in 'with'.) ( See link "Achchooda" also.)
Many women of this name were referred in the epic. One was mentioned in Udyoga parva, as wife of sage Richeeka and daughter of Gaadhi. One more also was mentioned in Udyoga parva, as one enjoyed by Naarada (different from the divine sage).
Sathyavathi was daughter of a Chedi king named Vasu (Also called Uparicharavasu, since he was given a flier by Indra and he flies anywhere with its help). she was given as an adopted daughter to a fisher-men chief Daasha. Daasha employed her to run a boat on the river Yamuna for the service of the passers by. Sathyavathi was said, in her previous birth, to be Achchoda, the daughter of one groups of the gods of Pithris named Baarhishadas.
Once a sage Paraashara went that way and fell for her beauty. He asked her to please him but she refused offering three reasons. One, she was a maiden and hence cannot accede to his request of pleasures; two, her body was stinking with the smell of fish; and three, that was a bright day then and union in an open place in a broad day light was not morally fit. The sage foiled all the three reasons by, 1) giving her a boon that she would remain a maiden even afterwards, 2) benedicting her that her body would spray out lotus smell that would spread upto one yojana (=4 krose or 8 miles or 13 kilometer. Hence she was thereafter called Yojanagandhi too. Gandhi=smelling) and 3)creating a dense due all around the river thereby causing a thick enclosure. She welcomed the sage and she soon begot a son instantaneously. The son was none other than the celebrated Vyaasa himself. Vyaasa went on penance assuring his mother about his presenting before her whenever she thought of him.
After many years, the king of Hasthipuram, Shanthanu went that way and felt the fragrance of her body from a very great distance. He followed that smell and found Sathyavathi. He was infatuated with her beauty and body odour. He asked her to marry him but she passed the issue to his father who refused to give her to Shanthanu stating that he wanted her son to become the king but it was impossible then as Shanthanu had already a son Devavratha, the heir apparent. Shanthanu did not want to deprive Devavratha of his lawful right to the throne and returned. But his passion towards Sathyavathi made him dull and sick. Devavratha learnt about his father's displeasure and discovered the reason too. He went to Daasha and requested to give Sathyavathi to his father, promising that he would forego the throne in the favor of her sons. But Daasa expressed doubts about the possibilities of Bheeshma's future sons raising any claims to the throne. Then Devavratha made it clear that he would not marry at all and he took a vow to that effect. The gods wondered at the gallant and young prince's tremendous vow and hailed him as 'Bheeshma'(=terrific). Since then he was known as Bheeshma.
Sathyavathi gave birth to two sons Chithraangada and Vichithraveerya. Chithraangada was killed by a Gandharva named Chithraangada. Vichithraveerya too died young and childless, leaving his two wives Ambika and ambaalika behind him. Then Sathyavathi asked Bheeshma to marry and beget children to safeguard the throne but he refused saying that he would never break his vow of celibacy.
Then Sathyavathi thought of Vyaasa and prayed to him. She ordered hom to beget sons from Ambika and Ambaalika. As the queens did not enjoy or tolerate the appearance and form of the sage, the first son born to Ambika, Dhritharaashtra, was blind and the second son born to Ambaalika, Paandu, was pale white. Sathyavathi convinced Ambika again but the queen sent her maid in her place. The maid served the sage sincerely and begot a son , the wise Vidura.
After the birth of the paandavas and the kouravas, Vyaasa advised Sathyavathi to retire to the forests for penance. Accordingly Sathyavathi retired to the hermitages in the woods, along with her daughters-in law, Ambika and Ambaalika. Her role was very crucial in the Mahaabhaaratham, as many of the future incidents were the results of her marriage.